#include<iostream>
#include<vector>
using namespace std;
class Solution 
{
public:
    int missingNumber(vector<int>& nums) 
    {
        int ret=0;
        for(int i=0;i<=nums.size();i++)
        {
            ret^=i;
        }
        for(auto num:nums)
        {
            ret^=num;
        }
        return ret;
    }
};

int main()
{
    return 0;
}